CAMRT Radiography Practice Exam

What is the typical SID distance recommended for imaging AC joints?

1. 150 SID

2. 180 SID

3. 200 SID

4. 220 SID

The correct answer is: 180 SID

The typical Source-to-Image Distance (SID) recommended for imaging acromioclavicular (AC) joints is 180 SID. This distance is preferred because it helps to minimize the magnification of the anatomy and enhances the sharpness of the radiographic image. By maintaining a longer SID, the divergence of the x-ray beam is reduced, allowing for better detail and improved visualization of the joint structures. It is important to use the appropriate SID as it has a direct impact on image quality. A shorter SID could lead to increased magnification and potential distortion of the anatomy, which may obscure relevant details needed for accurate diagnosis. In contrast, while longer SIDs of 200 or 220 are utilized in some specific imaging situations to obtain additional distance-related benefits, they are generally not standard for routine AC joint imaging, where 180 SID strikes a balance between image quality and practical workflow.